The research goal is to understand how transient receptor potential (TRP) channels sense temperature. In this project, the central hypothesis is that unique residues (domains) within the temperature-activated TRP channels enable these proteins to sense changes in temperature and to gate ion cun-ents through the plasma membrane. Specific functional domains of the temperature-activated ion channels TRPM8 and TRPV1 should be found by usage of large-scale random mutant libraries. Specific aim 1: screen large mutant libraries of the heat- and cold-activated ion-channels TRPV1 and TRPM8 to find mutations that specifically affect temperature-activation, but not chemical activation. This aim will test, if domains exist in these channels that are specifically required for temperature-activation. Specific aim 2: detailed electrophysiological examination of these mutants to verify screening results and to find out if temperature-mutations uncouple the mechanism of voltage-activation. This might shed light on the question, if voltage-activation underlies the mechanism of temperature-activation, as was previously proposed, but is still questioned. Specific aim 3: mutation of identified residues into all other 19 amino-acids to learn what specific molecular interactions are associated with the temperature-deficient phenotype. These experiments could give detailed insight into the molecular mechanism and lead to new, testable theories of the mechanism of temperature-activation. Chronic pain is associated with many different diseases and thermosensation represents a significant component of pain sensation. Therefore, a molecular understanding of thermosensation is important and relevant to the field of pain. I expect this study to significantly advance the understanding of how we sense temperature at the molecular level.